The present invention relates to internal combustion engines; more particularly, to devices for controlling systems in an internal combustion engine; and most particularly, to an improved hydraulic manifold assembly for controlling the flow of engine oil in variable activation and deactivation of valve lifters in an internal combustion engine, wherein air is automatically purged from the supply gallery and individual control galleries, and oil drainage there from is prevented.
In conventional prior art four-stroke internal combustion engines, the mutual angular relationships of the crankshaft, camshaft, and valves are mechanically fixed; that is, the valves are opened and closed fully and identically with every two revolutions of the crankshaft, fuel/air mixture is drawn into each cylinder in a predetermined sequence, ignited by the sparking plug, and the burned residue discharged. This sequence occurs irrespective of the rotational speed of the engine or the load being placed on the engine at any given time.
It is known that for much of the operating life of a multiple-cylinder engine, the load might be met by a functionally smaller engine having fewer firing cylinders, and that at low-demand times fuel efficiency could be improves if one or more cylinders of a larger engine could be withdrawn from firing service. It is known in the art to accomplish this by de-activating the valve train leading to pre-selected cylinders in any of various ways, such as providing special valve lifters having internal locks which may be switched off either electrically or hydraulically. Such switching conveniently performed via a hydraulic manifold that utilizes electric solenoid valves to selectively pass oil to the lifters on command from an engine control module (ECM). Such a manifold is referred to in the art as a Lifter Oil Manifold Assembly (LOMA).
A serious problem exists in adapting hydraulic control to valve deactivation. Such systems require hydraulic rigidity for proper operation and as such are highly intolerant of air in either the main gallery or the individual control galleries. Air in these galleries can increase the deactivation response time and also cause variation in response time. Both of these conditions can cause inaccurate activation or deactivation timing, resulting in loss of function and potentially catastrophic engine failure.
It is a principal object of the present invention to provide an improved solenoid-actuated hydraulic manifold assembly for controlling the hydraulic locking and unlocking of deactivatable valve lifters in an internal combustion engine, wherein any air present in the supply or control oil galleries at engine startup is automatically purged from the circuits and is actively prevented from re-entry during the periods of inactivity.
Briefly described, a hydraulic manifold assembly for variable actuation of engine valves in accordance with the invention includes oil flow passages, or galleries, formed therein. Typically, a riser providing engine oil under pressure communicates with a global supply gallery in the manifold assembly, from which pressurized oil is supplied selectively via an individual supply gallery to each variable actuator for each valve through the action of a solenoid valve disposed between the global supply gallery and each individual supply gallery. At engine startup, all galleries may be empty of oil, or partially filled. A global relief valve at the end of the global supply gallery opposite the oil riser leads back to the crankcase and is set to open at a pressure below the normal operation engine oil pressure. Air in the global supply gallery is thus purged immediately upon startup of the engine, and oil continues to be flowed actively throughout the global gallery at all times, the pressure therein being equal to the opening pressure of the relief valve. Further, each solenoid and gallery is provided with a low pressure relief valve leading back to the crankcase. When the solenoid valve is open, the pressure relief valve is closed; when the solenoid valve is closed, the pressure relief valve is open. A bleed orifice between the global supply gallery and each individual gallery continually bleeds oil under low pressure into each individual gallery, which purges initial air therein but is insufficient to actuate the deactivation mechanism. Further, each individual gallery is provided with anti-draining means to keep the gallery filled while the valve deactivation mechanism is inactive.